One relevant detail is that this was not a self contained device, it was for monitoring likelihood of seizures and had an external wireless interface. So my guess (this is pure speculation) on what happened is, the company owned the monitoring device, and the signals from the in-brain device were proprietary and encrypted. They couldn't force her to have surgery but they could take back the external interface which was their property, and without that the in-brain device did nothing. Then the patient agreed to surgery because there was no further benefit to keeping it in her head and probably greater health risks to doing so.